(1) Field of the Invention
This invention relates to disposal of solid waste disposal and particularly to a process for treating by-products of the lithium/sulfur hexafluoride reaction in order to prevent potential environmental problems and to reduce overall product costs.
(2) Description of the Prior Art
The reaction of lithium and sulfur hexafluoride is utilized as an energy source to power a torpedo. A mixture of lithium and sulfur hexafluoride are placed in the boiler portion of a torpedo and ignited using a charge of pure aluminum and potassium perchlorate. This produces heat to boil a working fluid which is used to drive the propeller of the torpedo. The spent fuel produced is primarily a solid cake of lithium sulfide and lithium fluoride, potassium fluoride and aluminum oxide with a small amount of unreacted lithium. Upon completion of a test with a torpedo, the spent fuel must be treated to render it environmentally acceptable safe level and for recycling to produce additional fuel components. Such a treatment is difficult since lithium reacts slowly in air and violently with water to produce hydrogen gas. In addition, lithium fluoride is both toxic and insoluble in most solvents. It has been proposed to fragment the solid by-product matrix with a pulsed high velocity water stream in order to provide ease for further treatment. This process is dangerous since hydrogen gas produced is dangerous besides lithium fluoride being toxic.
It has also been proposed to preliminarily treat the solid waste by-product to evaporate the lithium metal portion of the solid waste in an inert gas atmosphere at 500.degree. F. However, this process is dangerous and expensive.
U.S. Pat. No. 4,655,828 to Yates et al utilizes a solution of a Lewis acid in an organic solvent in order to dissolve the salt phase of the solid waste. While this process provides a means for recovering metallic lithium, it does not provide a means for treating the lithium sulfide and lithium fluoride portions of the solid waste. Other methods to extract lithium in some form have been described in the U.S. Patents such as U.S. Pat. No. 4,588,566 to Kluksdahl; U.S. Pat. No. 4,594,076 to Castrantas; U.S. Pat. No. 4,285,914 to Davidson; U.S. Pat. No. 3,523,751 to Burkert et al using different methods. However, none of these references addresses the extraction of other environmentally unsafe by-products besides lithium from the sold waste by-products from lithium-hexaflouride reaction.
It would be desirable to provide a process for treating the solid waste from a lithium/sulfur hexafluoride fuel reaction in order to produce an environmentally acceptable safe product, by extracting most of the compounds in the by-product and wherein at least a portion of lithium can be recycled to produce additional fuel.